http://www.erasme.org/VPNs-IPsec-multipoints-dynamiques
http://www.cisco.com/en/US/tech/tk583/tk372/technologies_configuration_example09186a008014bcd7.shtml
http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6586/ps6635/ps6658/DMVPN_Overview.pdf